Answer:
1.12g/mol
Explanation:
The freezing point depression of a solvent for the addition of a solute follows the equation:
ΔT = Kf*m*i
<em>Where ΔT is change in temperature (Benzonitrile freezing point: -12.82°C; Freezing point solution: 13.4°C)</em>
<em>ΔT = 13.4°C - (-12.82) = 26.22°C</em>
<em>m is molality of the solution</em>
<em>Kf is freezing point depression constant of benzonitrile (5.35°Ckgmol⁻¹)</em>
<em>And i is Van't Hoff factor (1 for all solutes in benzonitrile)</em>
Replacing:
26.22°C = 5.35°Ckgmol⁻¹*m*1
4.90mol/kg = molality of the compound X
As the mass of the solvent is 100g = 0.100kg:
4.9mol/kg * 0.100kg = 0.490moles
There are 0.490 moles of X in 551mg = 0.551g, the molar mass (Ratio of grams and moles) is:
0.551g / 0.490mol
= 1.12g/mol
<em>This result has no sense but is the result by using the freezing point of the solution = 13.4°C. Has more sense a value of -13.4°C.</em>
The element itself is Yttrium, which is a transition metal and not that reactive. Since it has 39 protons it will also have 39 electrons.
3s.f as that's what the numbers in the question are given to
So the answer is 0.978
The time the chocolate bar could power the laptop in hours is 0.00233 hrs.
Since 200 Calories of chocolate bar were burned to power the 100 Watt laptop, we need to find the number of joules on energy in 200 calories of chocolate bar.
Knowing that 4.2 Joules = 1 Calorie, then
200 Calories = 200 × 1 calorie = 200 × 4.2 Joules = 840 Joules
Since the power required by the laptop is 100 W = 100 J/s and Power, P = energy/time
so, time = energy/power
So, the time for the laptop to use 840 J of energy from the chocolate bar at a rate or power of 100 W = 100 J/s is
time = 840 J ÷ 100 J/s = 8.4 s
So, the time in hours is 8.4 s ÷ 3600 s/1 h = 0.00233 hrs (since 1 hr = 3600 s)
So, the time the chocolate bar could power the laptop in hours is 0.00233 hrs.
Learn more about time to power here:
brainly.com/question/17732603
